In recent television receivers for household use, for example, display devices that are provided with a liquid crystal panel as a front display unit are becoming the norm, as exemplified by liquid crystal display devices, with many advantages over conventional cathode-ray tubes, such as being thinner and lighter. Such liquid crystal display devices are provided with a backlight device that emits light and a liquid crystal panel that displays desired images by acting as a shutter for light from light sources provided on the backlight device. In television receivers, information such as characters, images, and the like included in image signals from television broadcasts are displayed on the display surface of the liquid crystal panel.
Backlight devices are largely divided into either direct-lit types or edge-lit types depending on the arrangement of light sources with respect to the liquid crystal panel, which is the object to be illuminated, but recent liquid crystal display devices commonly use edge-lit types, which are easier to make thinner than direct-lit types. In other words, an edge-lit backlight device is made thinner by arranging the light sources on a side of the liquid crystal panel, and a light guide plate provided with a light exiting surface (a light emitting surface) facing the non-display surface of the liquid crystal panel is used to provide light to the liquid crystal panel from the light sources.
In such an edge-lit backlight device as described above, light diffusing parts such as bumps that have prescribed patterns are provided in the light guide plate with respect to the non-light exiting surface, which is disposed so as to face the light exiting surface, in order to emit light towards the liquid crystal panel while guiding light from the light sources in a prescribed direction. In these backlight devices, a reflective sheet is provided so as to face the non-light exiting surface of the light guide plate in order to increase the usage efficiency of light emitted from the light sources, and light that goes outside the non-light exiting surface is reflected back towards the light guide plate.
In liquid crystal display devices such as those described above, a printed circuit substrate with electronic components mounted thereon for driving the liquid crystal panel, or a printed circuit substrate with electronic components mounted thereon for driving the light sources of the backlight device is usually attached to the outside of the bottom of the backlight device casing (external vessel) in order to make the liquid crystal display device more compact.
However, the reflective sheet and light guide plate are sequentially placed inside the backlight device casing. Thus, in such a backlight device, problems sometimes occurred such as uneven brightness leading to a reduction of light emitting quality. Specifically, in such a backlight device, a squeezing part (a part with recesses and protrusions) for attaching the printed circuit substrate described above is provided on the casing, and thus, sometimes slight level differences occurred at the base portion of this squeezing part, and this level difference pushed the reflective sheet inside the casing towards the light guide plate. This caused the reflective sheet to damage the light guide plate, especially in flat portions of the light guide plate where the light diffusing parts are not provided, and light progressing through the light guide plate was completely reflected by these damaged portions of the light guide plate and emitted towards the liquid crystal panel (the object to be illuminated). The result was that sometimes uneven brightness (uneven whiteness) occurred in which parts of the illumination light for the liquid crystal panel were brighter than other parts, causing a reduction in the light emitting quality of the backlight device and a reduction in display quality of the liquid crystal display device.
To address this, a configuration is proposed, as disclosed in Patent Document 1 below, for example, in which a large number of protective dots made of a resin are formed on the surface of the reflective sheet near the light guide plate in a conventional backlight device. In this conventional backlight device, the protective dots can prevent the light guide plate from being damaged even if the reflective sheet is pushed towards the light guide plate.